With rapid developments of information and communication technologies, the demand for wideband communications system based on a high-frequency band is sharply increasing. Accordingly, a technique for verifying and inspecting microwave devices, such as with antennas, is required.
As a method for inspecting the characteristics of antennas, a technique for imaging the electromagnetic fields of antennas attracts interest, and various scanning and optical techniques for implementing the imaging technique are being developed.
A known method is a technique of measuring an electromagnetic field using a scanning probe. However, the technique of measuring an electromagnetic field using a scanning probe requires a long measurement time, and it is difficult to design a probe for such measurement.
As another method, an optical indicator method using the electro-optical effect and the magneto-optical effect is known. However, the optical indicator method requires a material having the electro-optical effect or the magneto-optical effect, needs synchronization of an electromagnetic field with optical signals for measurement, has a limited bandwidth and/or requires an external magnetic field.